Electrospinning is a versatile technique for the production of small-diameter fibers of many natural and synthetic polymers. This includes biopolymers (DNA, gelatin), liquid crystalline polymers (polyaramid), textile fiber polymers (nylon) and electrically conducting polymers (polyaniline) etc. (J. of Macromolecular Science, 36(2): 169 (1997); J. of Biomedical Materials Research 72(1): 156 (20505); Nanotechnology 7(3): 216 (1996); Polymer 43(3): 775 (2002); Applied Physics Letters 83(20): 4244 (2003)). Electrospinning is a process in which ions are transferred to the gas phase by the application of a high electrical charge to a polymer solution in a liquid reservoir. Exposure of a small volume of electrically conductive liquid to an electric field causes the liquid to deform from the shape established by surface tension alone. As the voltage increases the force of the electric field approaches the surface tension of the liquid, resulting in the formation of a Taylor cone with convex sides and a rounded tip. When a threshold voltage is reached the slightly rounded tip of the cone inverts and emits a jet of liquid called a cone-jet or sheath-jet.
As the highly charged liquid jet stream travels in the air towards an electrically grounded collector it experiences bending and stretching effects due to charge repulsion and, in the process, becomes increasingly thinner. As the volatile solvent evaporates very fine polymer fibers, typically on the micro- or nano-scale, are collected on the grounded collector.
Current needle electrospinning techniques typically operate at flow rates between 1-10 mL/h, resulting in low throughput and deposition (i.e., polymer solidification). While slit-surface electrospinning offers a way to increase this output rate, this method tends to be unstable over longer periods of time and demonstrates meniscus growth. Thus, there is a need for a stable, high throughput slit-surface electrospinning process that provides longer run times and reduces meniscus formation.